Large-area plasma enhanced chemical vapor deposition (PECVD) has been considered as one of the most important apparatus to make the energy costs of thin film silicon solar cells competitive with grid electricity in that it can effectively improve the production throughput and hence reduce the production costs because of the characteristics of larger substrate and higher deposition rate. However, the non-uniform discharge caused by the standing wave effect imposes limitation on achieving uniform thin film deposition in large-area PECVD. Up to date, several attempts have been proposed to resolve the technological bottleneck, including lens-shaped electrode, ladder-shaped electrode or dual comb-type electrodes with phase modulation, superposition of two standing waves that are alternatively ignited and multiple feeding points. Although all the above-mentioned means could more or less improve the uniformity of plasma discharge, most of them might be limited to a fixed frequency and a specific operation window because they are based on the design concept that the configuration of special shaped electrode or the number and arrangement of feeding points is designed for a given standing wave pattern. Nevertheless, for radio-frequency (RF) and very-high-frequency (VHF) plasmas, the standing wave pattern depends on the wavelength of electromagnetic wave in the plasma region, which could be influenced by a variety of experimental parameters, such as frequency, discharge gap, power, pressure, and gas compositions. The actual wavelength in plasma ranges from 12% to 60% of that in vacuum.
Consequently, it is in need to develop a new plasma generating apparatus which is capable of providing large-area uniform plasma in its discharge region.